In the art of magnetic resonance imaging metal-comprising implants are known to pose issues that require careful consideration. Implants like internal fixations, artificial joints, or pacemakers are typically made of highly electrically conductive metal, in which eddy currents may be excited inside a scanning unit of a magnetic resonance imaging system, mainly caused by the radio frequency magnetic excitation field B1 required for resonantly exciting nuclei of or within a subject of interest to be examined.
Magnetic resonance imaging near metal is typically compromised by susceptibility issues, locally degrading the magnetic fields used for image formation. In diagnostic magnetic resonance imaging scans, the susceptibility of the metal parts can cause magnetic resonance signal pile-up, signal voids and other geometric distortions, resulting in image artifacts.
Besides the generation of magnetic resonance imaging artifacts, the eddy currents excited in metal-comprising implants may substantially contribute to the specific absorption rate (SAR) that the subject of interest is exposed to during a magnetic resonance examination, and that is subject to limits from safety regulation requirements.
With aging population and an increasing number of patients carrying metal-comprising implants, the need for magnetic resonance imaging of soft tissue in the presence of metal increases.